Removable programmable conductor memory card and associated read/write device and method of operation
A removable memory card and an associated read/write device and its method of operation are disclosed. The memory card may be formed of a sheet of chalcogenide glass material which has memory storage locations therein defined by the locations of conductive read/write elements of the read/write device.
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The invention relates to non-volatile memory devices using programmable conductor random access memory (PCRAM) arrays.
BACKGROUND OF THE INVENTIONThere is a trend toward use of removable non-volatile memory devices such as flash memory devices in digital cameras and other devices which benefit from removable non-volatile memory. Conventional non-volatile memory devices typically have limited density, high manufacturing cost, and high power consumption. A lower cost alternative to flash and other conventional removable non-volatile memory devices is desirable.
SUMMARYIn one aspect, the invention provides a programmable conductor random access memory (PCRAM) apparatus and method of operation which uses a removable PCRAM memory card comprising a programmable conductor material, e.g. a chalcogenide glass, layer containing a plurality of data storing memory elements. A housing into which the card can be inserted contains a read/write assembly containing conductive elements which define and/or align with previously defined memory elements of the card. The conductive elements are in removable contact with the memory cells of the card and are used to read and write data from and to the memory elements of the card.
The invention also provides a removable card formed of a programmable conductor material, e.g. chalcogenide glass, which can be used with a read/write assembly to define and program memory elements within the programmable conductor material.
The invention also provides a removable memory card formed of a programmable conductor material, e.g. a chalcogenide glass, which has a plurality of memory elements defined therein and which can be used for temporary or permanent storage and in which both temporary and permanent storage cells can simultaneously coexist on the same memory card.
The foregoing and other features and advantages of the invention will become more apparent from the detailed description of the exemplary embodiments of the invention given below in connection with the accompanying drawings in which:
FIG. 2A and
The lower electrodes 105 are connected to tungsten plugs 104. The upper electrodes 103 are commonly connected to a cell plate 106. The arrangement is similar to that used in a conventional DRAM, except that the cell capacitors normally provided in a DRAM are replaced by the programmable conductor memory element 110 formed by the programmable conductor material layer 102 and the upper 103 and lower 105 electrodes. For purposes of simplifying further discussion, the programmable conductor material layer will be assumed to be a doped chalcogenide glass layer, but it should be understood that any programmable conductor material can be used.
Normally the programmable conductor glass memory element 110 is in a higher resistance state, but it can be programmed to a lower resistance state by application of a suitable voltage across memory element 110. Access transistors 111 are connected to separate wordlines (not shown) which are activated to couple the memory elements 110 to the bit line 116, and thereby apply suitable voltages across the memory element 110 for both programming the memory element to a lower resistance state as well as erasing a memory element back to a higher resistance state.
The lower resistance state of the memory elements 110 may occur due to the growth of a conductive dendrite within or on the surface of the chalcogenide glass layer 102 by the voltage applied to the conductors 103, 105. This dendrite is non-volatile in that it remains when the voltage across the cell 101 is removed.
The lower resistance state of the memory element 110 may occur due to the fact that the cell 101 has grains or quantum dots which span the upper 103 and lower 105 electrodes of the cell 101. These grains may or may not be metallic in content. When a potential is applied across the cell 101, metal ions migrate into these structures and lower the resistivity of the cell 101 by clustering in/on the grains and ultimately connecting the grains. A reversal in the potential across the cell 100 essentially pushes the metal ions out of these grains, thus increasing the resistance of the cell 101. Thus, to return the cell 101 to a higher resistance state a reverse voltage at least equal to the program voltage required to program the cell 101 to a lower resistant state is applied across the conductors 103, 105.
A memory element 110 is typically read by applying a voltage across it which is less than that required for writing the memory element 110 to a lower resistance state. This read voltage is discharged through the resistance of the memory element 110 and the discharging voltage is read at some point to determine the high or low resistance state of the memory element 110 and thus a stored binary value.
Although
The present invention utilizes the overall memory cell 101 architecture shown in
The card 200 is passive in that it does not contain any access transistors, bit lines or wordlines, but is dedicated to the programmable conductor material 201 in which areas (e.g., 202) are available for use as memory cells. It should be noted that although
Another characteristic of one embodiment of a memory card 200, shown at
In order to define the locations of the PCRAM elements 202 in the memory card 200, as well as to read from and write to those memory elements 202, access transistors, bit lines and word lines of a read/write assembly necessary to operate the memory elements 202 are contained within the read/write device illustrated in
The pivot arms 340 shown in greater detail in
The memory card 200 can be released by pressing a button 354, which connects with a rod 346 having on one end an incline surface 356 against the bias of spring 348. By pushing on button 354, the incline surface 356 raises a rod 344 which pushes pivot arms 340 against the bias force, causing them to be withdrawn from the memory card 200. When the memory card is released by the pivot arms 340, the bias on an end element 350 causes the element 350 to push the memory card 200 partially out of opening 303, where it may be grasped and removed by a user.
A read/write assembly 358 is also provided within housing 302 and is illustrated in perspective view in FIG. 4. The read/write head assembly 358 includes a plurality of upwardly projecting conductive elements 304. At shown in
As also illustrated in
It should be noted that although the conductive elements 304 have been illustrated in the various figures as having a pointed or tipped configuration, they may in fact be constructed as rounded bumps or flat surfaces as well, the important aspect being that the conductive elements 304 provide one of the two required electrodes on opposite sides of a programmable conductor material 201 of card 200 suitable to provide, with the common electrode 204, appropriate voltages across the programmable conductor material 201 to define memory elements 202 which can read, written, and erased.
When the memory card 200 is locked into position relative to the read/write assembly 358, alignment is achieved between the card 200 and the read/write assembly 358 so that a memory card 200 which is has been programmed in one housing 302 can be removed and inserted into another like housing 302 and be properly read/written.
To further enhance the ability of the memory card 200 to be properly aligned relative to the conductive elements 304 of different read/write assemblies 358 provided in differing housings 302, it may be desirable to provide a more sophisticated control system for automatically aligning the memory card 200 with the read/write assembly 358.
FIG. 7 and
The controller 417 can control the motors 403 to move the card 200 in a removal as well as insertion direction as illustrated by the arrows of FIG. 7. Pushing removal button 354 in this embodiment closes a card removal switch 413, which causes controller 417 to release the card 200 by driving the rollers 405 in a card removal direction. Controller 417 can also fine tune the location of the card 200 within the housing 302 to ensure that the card 200 is properly aligned with respect to the conductive elements 304 of read/write assembly 358. This is done by controlling both the motors 403 which control the insertion and removal of the card 200, and its terminal position in the insertion/removal direction, as well as an additional motor 407 which drives a roller 409, which in turn is coupled to a frame 401 on which the motors 403 are mounted.
The frame 401 is driven by motor 407 in a lateral direction relative to the card insertion and removal direction. Thus, by appropriately controlling motor 407 as well as the motors 403, controller 417 can position an inserted card 200 in a precise longitudinal and lateral position relative to the read/write conductors 304 of the read/write assembly 358.
In addition, as shown in
The controller 417 illustrated in
An additional feature of the invention is the ability to store information in the memory card 200 as temporary or permanent data. For temporary data storage appropriate voltages are applied to bit lines, cell plate and gate of the access transistor of a memory cell. The voltage chosen will cause a memory element 202a, which is in an at rest higher resistance state, to be programmed to a lower resistance state. For example, for a chalcogenide glass composition of Ge25:Se75 doped with silver a voltage V1 (
A user has a choice of causing read/write assembly 358 to change one or more memory elements 202 from semi-volatile (re-writable) state to permanent (Read-Only Memory) state. This can be done by adjusting the write voltage upward to range between 1.5-3.0 volts for permanent storage, compared to the 0.25 volts used for semi-volatile storage. Also, some memory elements of the memory card 200 can be written permanently with the high voltage and used as a ROM, while other memory elements 202 of the same memory card 200 can be written as semi-volatile (re-writable) memory elements, or all memory elements 202 of a card 200 may be permanent storage memory elements or all memory elements 202 may be temporary storage memory elements.
While the invention has been described and illustrated with reference to specific exemplary embodiments, it should be understood that many modifications and substitutions can be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be considered as limited by the foregoing description but is only limited by the scope of the appended claims.
Claims
1. A programmable conductor apparatus, comprising:
- a memory card comprising a programmable conductor material capable of providing a plurality of memory storage areas; and
- a read/write assembly having a plurality of conductive elements for contacting said memory card at said plurality of memory storage locations to enable read/write operations at said memory storage areas.
2. A programmable conductor apparatus as in claim 1 further comprising a housing within which said read/write assembly is located, said housing including an opening for receiving said memory card and an internal mechanism for positioning a memory card relative to the conductive elements of said read/write assembly.
3. The apparatus of claim 1 wherein said programmable conductor material comprises a chalcogenide glass.
4. The apparatus of claim 1 wherein said memory card has predefined memory storage areas.
5. The apparatus of claim 4 wherein at least some of said predefined memory storage areas are programmed permanent memory storage areas.
6. The apparatus of claim 4 wherein at least some of said predefined memory storage areas are temporary storage areas.
7. The apparatus of claim 4 wherein at least some of said predefined memory storage areas are permanent storage areas and at least some of said predefined memory storage areas are temporary storage areas.
8. The apparatus of claim 3 wherein said chalcogenide glass comprises between 20 to 30 percent germanium and between 70 to 80 percent selenium, and is doped with silver.
9. The apparatus of claim 1 wherein said memory card further comprises a conductive layer extending over a first surface of said card, said conductive elements contacting a second opposite surface of said card.
10. The apparatus of claim 2 wherein said housing further comprises a door at said opening.
11. The apparatus of claim 1 wherein said conductive elements comprise metal elements.
12. The apparatus of claim 11 wherein said conductive elements contain silver.
13. The apparatus of claim 12 wherein said conductive elements are connected to respective access transistors through conductive polysilicon elements.
14. The apparatus of claim 1 wherein said read/write assembly further comprises an access transistor for coupling a respective conductive element to a digit line, in response to an enabling voltage provided to a word line to which a gate of said access transistor is connected.
15. The apparatus of claim 2 wherein said memory card further comprises an alignment structure and said housing further comprises an internal structure which cooperates with said alignment structure to align said memory card relative to said read/write assembly.
16. The apparatus of claim 15 further comprising a position control mechanism within said housing which senses the location of said card relative to said read/write assembly and adjusts the relative position of said memory card and read/write assembly to achieve alignment.
17. The apparatus of claim 16 wherein said alignment structure comprises a pattern of preprogrammed memory storage areas, said position control mechanism including a pattern of conductive elements for reading said preprogrammed memory storage areas and adjusting said relative position until said pattern of preprogrammed memory storage areas is properly read.
18. The apparatus of claim 16 wherein said alignment structure comprises optically readable alignment marks provided on said memory card, said position control mechanism including an optical reader for reading said optical marks.
19. The apparatus of claim 15 wherein said alignment structure comprises at least one mechanical feature on said memory card which engages with at least one mechanical element within said housing when said memory card is aligned with said read/write assembly.
20. The apparatus of claim 15 further comprising a circuit for preventing operation of said read/write assembly until alignment is achieved.
21. A memory card comprising:
- a sheet of programmable conductor material which can be programmed to define a plurality of storage areas, each having a resistance state corresponding to a stored logic value, said sheet being configured to be insertable into and removed from a card reading device.
22. A memory card of claim 21 wherein said programmable conductor material comprises a chalcogenide glass.
23. A memory card of claim 22 wherein said chalcogenide glass comprises between 20 to 30 percent germanium and between 70 and 80 percent selenium, and is doped with silver.
24. A memory card of claim 21 wherein said memory card has predefined memory storage areas.
25. A memory card of claim 24 wherein at least some of said predefined memory storage areas are programmed permanent memory storage areas.
26. A memory card of claim 24 wherein at least some of said predefined memory storage areas are temporary storage areas.
27. A memory card of claim 24 wherein at cast some of said predefined memory storage areas are permanent storage areas and at lest some of said predefined memory storage areas are temporary storage areas.
28. A memory card of claim 21 wherein said removable memory card further comprises a conductive layer extending over a first surface of said card, said conductive elements contacting a second opposite surface of said card, a second opposite surface of said card being adapted to be connected to a read/write assembly.
29. A memory card of claim 21 wherein said memory card further comprises an alignment structure for aligning said card with a read/write assembly.
30. A memory card of claim 29 wherein said alignment structure comprises a pattern of predetermined memory storage areas preprogrammed with a program code.
31. A memory card of claim 29 wherein said alignment structure comprises optically readable alignment marks.
32. A memory card of claim 29 wherein said alignment structure comprises a mechanical feature on said memory card.
33. A card read/write structure for a programmable conductor memory card, said structure comprising:
- a read/write assembly, said assembly comprising a plurality of conductive elements for respectively contacting programmable conductor storage areas of said memory card to enable read/write operations at said areas.
34. A structure of claim 33 further comprising a housing having a card entry opening, said read/write assembly being located within said housing.
35. A structure of claim 33 wherein said conductive elements comprise metal elements.
36. A structure of claim 33 wherein said conductive elements comprise silver elements.
37. A structure of claim 33 wherein said read/write assembly further comprises an access transistor for coupling a respective conductive element to a digit line, in response to an enabling voltage provided to a word line to which a gate of said access transistor is connected.
38. A structure of claim 34 further comprising an internal structure within said housing which cooperates with an alignment structure on a memory card to provide alignment of a memory card relative to said read/write assembly.
39. A structure of claim 38 further comprising a position control mechanism within said housing which senses the location of said card relative to said read/write assembly and adjusts the relative position of said memory card and read/write assembly to achieve alignment.
40. A structure of claim 39 wherein said position control mechanism includes a pattern of conductive elements at said read/write assembly for reading a program code provided at an alignment storage area of a memory card, said position control mechanism adjusting relative position of a memory card and read/write assembly until said program code is properly read.
41. A structure of claim 39 wherein said position control mechanism includes an optical reader for reading optical alignment marks on a card.
42. A structure of claim 38 wherein said internal structure comprises at least one mechanical element within said housing which engages with a least one mechanical feature on said memory card to produce alignment.
43. A structure of claim 34 further comprising a latch mechanism for holding a card within said housing.
44. A structure of claim 43 further comprising a release mechanism for releasing said latch mechanism to allow removal of a card from within said housing.
45. A method of operating a programmable conductor card, said method comprising:
- providing a memory card comprising a programmable conductor memory material;
- defining a plurality of memory storage areas with a plurality of conductive elements; and
- engaging said card with said plurality of conductive elements to read or write data from or to said memory storage areas in said memory card.
46. The method of claim 45, further comprising aligning said memory card with said plurality of conductive elements before commencing a read or write operation.
47. The method of claim 45, further comprising writing to at least one of said memory storage areas in a manner which causes temporary data storage.
48. The method of claim 45, further comprising writing to at least some of said memory storage areas in a manner which causes permanent data storage.
49. The method of claim 45, further comprising writing to at least some of said memory storage areas in a manner which causes temporary data storage and writing to some of said memory storage areas in a manner which causes permanent data storage.
50. The method of claim 46, further comprising forming an alignment structure on said memory card and aligning said memory card using said alignment structure.
51. The method of claim 50 wherein said alignment structure comprises preprogrammed memory storage areas of said card.
52. The method of claim 50 wherein said alignment structure comprises optical alignment marks.
53. A processor apparatus, comprising:
- a processor;
- a programmable conductor memory system connected to said processor, said memory system comprising:
- a read/write assembly located inside a housing and having a plurality of conductive elements for contacting respective memory storage areas of a programmable conductor material memory card at said plurality of memory storage areas to enable read/write operations at said memory storage areas;
- said housing including an opening for receiving a said memory card and an internal mechanism for positioning a received memory card relative to the conductive elements of said read/write assembly.
54. The processor apparatus of claim 53 further comprising said memory card.
55. The processor apparatus of claim 54 wherein said programmable conductor material comprises a chalcogenide glass.
56. The processor apparatus of claim 54 wherein said memory card has predefined memory storage areas.
57. The processor apparatus of claim 56 wherein at least some of said predefined memory storage areas are programmed permanent memory storage areas.
58. The processor apparatus of claim 56 wherein at least some of said predefined memory storage areas are temporary storage areas.
59. The processor apparatus of claim 56 wherein at least some of said predefined memory storage areas are permanent storage areas and at least some of said predefined memory storage areas are temporary storage areas.
60. The processor apparatus of claim 57 wherein said chalcogenide glass comprises between 20 to 30 percent germanium and between 70 to 80 percent selenium, and is doped with silver.
61. The processor apparatus of claim 54 wherein said memory card further comprises a conductive layer extending over a first surface of said card, said conductive elements contacting a second opposite surface of said card.
62. The processor apparatus of claim 53 wherein said housing further comprises a door at said opening.
63. The processor apparatus of claim 53 wherein said conductive elements comprise metal elements.
64. The processor apparatus of claim 53 wherein said conductive elements comprise silver elements.
65. The processor apparatus of claim 53 wherein said read/write assembly further comprises an access transistor for coupling a respective conductive element to a digit line, in response to an enabling voltage provided to a wordline to which a gate of said access transistor is connected.
66. The processor apparatus of claim 54 wherein said memory card further comprises an alignment structure and said housing further comprises an internal structure which cooperates with said alignment structure to align said memory card relative to said read/write assembly.
67. The processor apparatus of claim 66 further comprising a position control mechanism within said housing which senses the location of said card relative to said read/write assembly and adjusts the relative position of said memory card and read/write assembly to achieve alignment.
68. The processor apparatus of claim 67 wherein said alignment structure comprises a pattern of preprogrammed memory storage areas, said position control mechanism including a pattern of conductive elements for reading said preprogrammed memory storage areas and adjusting said relative position until said pattern of preprogrammed memory storage areas is properly read.
69. The processor apparatus of claim 67 wherein said alignment structure comprises optically readable alignment marks provided on said memory card, said position control mechanism including an optical reader for reading said optical marks.
70. The processor apparatus of claim 66 wherein said alignment structure comprises at least one mechanical feature on said memory card which engages with at least one mechanical element within said housing when said memory card is aligned with said read/write assembly.
71. The processor apparatus of claim 66 further comprising a circuit for preventing operation of said read/write mechanism until alignment is achieved.
72. A programmable resistance memory card, comprising:
- a programmable resistance material layer capable of defining a plurality of programmable memory storage areas spaced about said layer, said layer having a first surface which is electrically engageable with conductive elements of a conductor assembly for operating said memory storage areas.
73. The memory card of claim 72, further comprising:
- a bottom electrode attached to a second surface of said layer.
74. The memory card of claim 73, wherein said bottom electrode is a common electrode for said memory storage area.
75. The memory card of claim 72, wherein said memory storage areas comprise at least one of temporary and permanent memory storage.
76. The memory card of claim 72, wherein said layer comprises chalcogenite.
77. The memory card of claim 72, wherein said layer comprises between 20-30 percent germanium, between 70 and 80 percent selenium, and is doped with silver.
78. The memory card of claim 73, wherein said bottom electrode further comprises silver.
79. The memory card of claim 73, wherein said bottom electrode further comprises tungsten.
80. The memory card of claim 72, wherein said layer further comprises alignment areas.
81. The memory card of claim 80, wherein said alignment areas are formed as memory storage areas programmed with a pattern.
82. The memory card of claim 81, wherein said alignment areas are formed as alignment marks.
83. The memory card of claim 72, wherein said memory card has active circuit elements.
84. The memory card of claim 72, wherein at least some of said memory storage areas are non volatile.
85. The memory card of claim 72, wherein said first surface of said card is adapted to directly contact said conductive elements.
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Type: Grant
Filed: Feb 20, 2002
Date of Patent: Jan 25, 2005
Patent Publication Number: 20030156467
Assignee: Micron Technology, Inc. (Boise, ID)
Inventors: Terry L. Gilton (Boise, ID), Trung T. Doan (Boise, ID)
Primary Examiner: Trong Phan
Attorney: Dickstein Shapiro Morin & Oshinsky LLP
Application Number: 10/077,784